Method of making a knife



June 29, 1965 J. N. CHRISTIAN ETAL 3,191,460

I METHOD OF MAKING A KNIFE Filed July '7. 1961 2 Sheets-Sheet lINVENTORS JOfEPH M (HAP/5774M kWh 4Z0 4. MA/E5 %%TORNEY June 29, 1965Filed July 7. 1961 J. N. CHRISTIAN ETAL 3,191,460

METHOD OF MAKING A KNIFE 2 Sheets-Sheet 2 IMF/1V6 NOZZlf INVENTORS/0.5E/// 1V- (WAVE/VAN HOWJKD 4. JOA/FS United States Patent 3,191,460METHOD OF MAKING A KNIFE Joseph N. Christian and Howard A. Jones,Oneida, N. Y., assignors to Oneida Ltd., Oneida, N.Y., a corporation ofNew York Filed July 7, 1961, Ser. No. 121,781 3 Claims. (Cl. 76-104)This invention relates to the manufacture of knives.

More particularly, the invention is concerned with knives of the hollowhandled type and with the securing of the knife blade to the handle.Knives of this type have customarily been manufactured by placingso-called Sauerei'sen cement in the handle, inserting the blade tanginto the handle and then placing the blade and handle in a holdingfixture .and baking to set the cement. The cement once set cannot besoftened, is difiicult to clean off, is abrasive in character andporous. It is also unsuited to high speed automatic production methods,due to its irreversible setting action.

It is an object of the present invention to provide an improved tangholding material and method of assembly of the knife and handle,eliminating the deficiencies above mentioned.

. While attempts have been made to utilize thermoplastic materials suchas various synthetic resins as part or all of the filling and holdingmaterial for securing the tang within the handle of a knife, theseefforts have met with only limited success, due to difiicultiesexperienced in properly filling the handle with the synthetic resin, andalso due to casting stresses and voids created by shrinkage during thesetting process.

It is an object of the present invention to provide a structure of tangand handle which eliminates the creation of voids .and otherdifiic-ulties due to contraction upon setting.

A further object is to provide a method for filling the knife handlewhich is suitable for high speed mass production manufacture and insuresagainst looseness and objectionable voids. t

A knife construction and method of manufacturing the same will now firstbe described withreference to the accompany-ing drawing and the featuresforming the invention will then be more particularly pointed out in theappended claims.

In the drawing:

FIG. 1 is an exploded isometric showing a knife and hollow handle forproducing .a knife according to the method of the invention;

FIG. 2 is an isometric of the completed knife;

FIG. 3 is a section on the line 33 of FIG. 2;

FIG. 4 is a section on the line 4-4 of FIG. 2;

FIGS. 5 and 6 .are outline views, showing different configurations ofthe handle which may be utilized in the knife of the invention; and

FIG. 7 is a schematic view illustrating the cycle for producing .a knifeaccord-ing to the method of the invention.

Apart from certain manufacturing problems which will be mentionedlatter, the primary difiiculty in the formation of a knife by means of asynthetic resin filling the hollow handle and surrounding the blade tanghas been that the suitable resins from the standpoint of rapidproduction cycle, low cost and suitable mechanical properties aretypified by polystyrenes of various types which have considerable moldshrinkage as well as shrinkage after molding, and the coefiicient ofthermal expansion may be rela tively high as compared with most metals.

The mold shrinkage may approximate .004 in./ in. (the usual range beingfrom about .002-.006 in./in.). In consequence, when the handle and bladehaving a tang of usual configuration are assembled together and the3,191,460 Patented June 29, 1965 "ice space within the handle around thetang and elsewhere is filled with molten polystyrene and then thepolystyrene is allowed to set, the shrinkage involved in setting tendsto open up pockets at unpredictable locations and typically art thejoint between blade and handle, thus creating the possibility of theentrance of water and food particles and bacterial action of anunsanitary character, as Well as causing a weakening of the joint.Additional shrinkage occurring after molding may reach a magnitude of.001 in./in. *or somewhat more, aggravating any faulty condition due tomolding and in addition a composite plasticmetal structure is subjectedto stresses resulting from the fact that the coeificient of thermalexpansion of the plastic may be approximately double that of the metal.Under these conditions, the holding action of the synthetic resinbetween tang and handle may be of a localized and imperfect characterand the local failure or cracking of the plastic which occurs in anunpredictable manner after the lapse of an unpredictable time may resultin a loose handle with progressive increase of this looseness withcontinued use. For these reasons, prior to the present invention it hasnot been found practical to produce a polystyrene or similar syntheticresin to fill a hollow knife handle in a satisfactory manner.

In a preferred construction according to the present invention, theblade 1 has a bolster 2 for abutting against the handle and a tang 3which is of tapered form, being wide at its tip and narrowing graduallyas it approaches the bolster or butt end of the blade. The handle 4 maybe formed of stainless steel, brass or other metals and may have agenerally trapezoidal shape as shown in FIGS. 1 and 2, the contractedend adjacent the bolster being sufiiciently large as to admit theenlarged end of the tang 3. The handle may also have other outlines asindicated in FIGS. 5 and 6, the selection of particular contours beingmade from considerations of design and aesthetic appeal and notaffecting in any substantial way the molding and holding action.

While the synthetic resin as a whole will have a mold shrinkage of theorder of .004 in./in. as above stated, it has been found possible byutilizing a tang of the type indicated in conjunction with a suitablehollow handle and appropriate manufacturing technique, to produce aknife in which the mold shrinkage around the tang is eliminated and togo even further and to produce an actual expansion of the syntheticresin as it sets, in the space around the tang immediately adjacent thebolster. In this way, all looseness of holding which might progressivelyincrease in use and finally render the knife useless as well as allunsanitary open spaces adjacent the bolster are completely eliminated.Thus, when a knife of the type shown in FIGS. 1 and 6 is cut through soas to permit removing the hollow handle and the examination of thesurface of the polystyrene within it, it may be found that somelooseness will exist adjacent the butt end of the handle as Well as acertain amount of pitting and checking of the plastic in this area,while in the area at the narrow part of the handle surrounding the tangand adjacent the bolster, the synthetic resin will have thecharacteristic shiny molded finish, indicating its having been forcedunder pressure against the metal of the hollow handle as it set. It willbe noted that the net shrinkage at any section plane through the handlesuch as the plane of FIG. 3 is the net effect of the local moldshrinkage of the plastic within that plane, as increased by flow ofmaterial out of this plane or counteracted by flow of material into thisplane.

As is apparent from the geometry of the situation, the longitudinalshrinkage (parallel to the tang axis) will far exceed the transverseshrinkage (at right angles to the tang axis). The longitudinal shrinkageinvolves movement of plastic along the tang and this fact is utilized tocounteract and even reyerse the effect of transverse shrinkage aroundthe tang. As will be apparent, as soon as the plastic has suflicientlyset, it grips around the enlarged end of the tapered tang andlongitudinal shrinkage from this point on can only have the effect offorcing the plastic around the tang toward the knife bolster. Thislongitudinal shrinkage movement counteracts the transverse shrinkagearound the tang and to a suificient extent so that the material adjacentthe bolster and for a considerable way down the tang may actual-1y beexpanded and, hence, be under compression as it sets.

Prior techniques utilized in attempts to manufacture cutlery and similararticles of the type to which the present invention is directed have metwith limited success or no success whatever, due to the'absence ofsuitable techniques for relating assembly operations in a manner so asto obtain proper interaction between the synthetic resin and the handleand blade components and the absence of suitable techniques forobtaining a practical molding cycle. Thermoplastic synthetic resinmachines fall basically into three categories: injection moldingmachines, which inject heated thermoplastic into a die cavity underextremely high pressures (10,000 to 20,000 p.s.i.); extruding machineswhich produce sheet tubing, etc. by extruding heated thermoplasticthrough a suitably shaped dieand calender rollers which mechanicallywork thermoplastic masses to produce a sheet. There has been no chilled(as by a blast of cold air) and then to station 4 where it isdischarged. The handle is inserted at station 5 and station 6 may beidle. A typical index time may be one second and a typical filling time1.4 second, for anoverall cycle of 2.4 seconds, corresponding to aproduction of fifteen hundred pieces per hour, utilizing generallystandard indexing equipment. As will be understood, the indicatedoperations at the various stations all take place at each indexingmovement and as will be apparent to those skilled in the art, the timeintervals involved are entirely suitable with relation to thecharacteristics of the thermoplastic resin which is used.

With respect to the filling operation at station 1, as soon 7 as theindexing movement has been completed, the hanv tang, so that theinsertion of the tang displaces synthetic previous equipment ortechnique for filling a hollow handle with thermoplastic synthetic resinin a manner so as to permit a suitable molding cycle. The filling of thehandle by discharging melted plastic in a measured amount from a spoutis not suitable, due to entrapment of air in a cycle of any rapidity anda lack of control over the thermoplastic material in slower cycles. Thepresent invention provides a handle filling methotd of novel characterconsistent with a satisfactorily rapid cycle.

In accordance with the invention, thermoplastic resin is deposited in ahandle by a nozzle located, to begin with, close to the bottom of thehandle (as, for example, a quarter inch therefrom) and the nozzle andhandle are then moved apart at a regulated speed, corresponding to therate of filling of the handle so that entrapment of air (which wouldresult from too great separation between the nozzle and surface of theliquid plastic) is avoided, while at the same time undue hydraulicpressure (which would result from the immersion of the nozzle below thesurface of the liquid plastic) is also avoided. The nozzle may besupplied by otherwise standard injection molding equipment but it willbe observed that it operates against substantially atmospheric pressureas compared with the extremely high pressures encountered in injectionmoldmg.

A typical operating cycle is shown in a schematic manner in FIG. 7 ofthe drawing, and may involve the use of an index table of usual typehaving eight positions and rotating through at each step, at intervalssuch as about two or three seconds and corresponding to a productionrate of about fifteen hundred pieces per hour. Using a typical eightposition indexing table 10, having eight locations as shown, the cyclemay be, as follows:

The blade is loaded in a suitable holder at station 7, passes through anidle station 8 to station 1 where itis filled with the thermoplastic,thence to station 2 where the blade is inserted, thence to station 3where the handle is resin and squeezes it out between handle andbolster, finally cutting it off as bolster and handle engage. Afterchilling, the extruded plastic at this point is readily broken off andno finishing operation is ordinarily required.

What is claimed is:

1. Method of forming hollow handled cutlery which comprises injectingmelted thermoplastic synthetic resin having substantial mold shrinkagethrough a nozzle into the handlecommencing at a point close to thebottom of the handle and moving upwardly so as to keepthe nozzlesubstantially at the level of the synthetic resin as the handle isfilled, inserting the end of the tapered tang of a knife blade, whichtang is thicker at its said end, in the handle so as to displace some ofthe synthetic resin therefrom and bring the bolster of the blade againstthe upper edge of the hollow handle so as substantially to close off thespace within the handle, and then setting the synthetic resin so as tocontract the same longitudinally of the handle and compress the samearound the tang, thereby eliminating transverse mold shrinkage aroundthe tang. 2. Method according to claim 1, in which the said resin ispolystyrene.

3. Method according to claim 1, in which the said resin is polystyrenehaving about .004 in./in. mold shrinkage.

References Cited by the Examiner UNITED STATES PATENTS 6,482 5/49 Ropes76-104 103,278 5/70 Bailey 30-343 1,030,321 6/12 Muller et al. 76-1041,167,404 1/16 Hoch 76-104 2,072,581 3/37 Curtis 30-343 2,533,986 12/50Atterbury 141-263 X I FOREIGN PATENTS 59,078 5/ 13 Austnia.

FRANK E. BAILEY, Primary Examiner.

EDWARD V. BENHAM, FRANK H. BRONAUGH,

Examiners.

1. METHOD OF FORMING HOLLOW HANDLED CULTERY WHICH COMPRISES INJECTING MELTED THERMOPLASTIC SYNTHETIC RESIN HAVING SUBSTANTIAL MOLD SHRINKAGHE THROUGH A NOZZLE INTO THE HANDLE COMMENCING AT A POINT CLOSE TO THE BOTTOM OF THE HANDLE AND MOVING UPWARDLY SO AS TO KEEP THE NOZALE SUBSTANTIALLY AT THE LEVEL OF THE SYNTHETIC RESIN AS THE HANDLE IS FILLED, INSERTING THE END OF THE TAPERED TANG OF A KNIFE BLADE, WHICH TANG IS THICKER AT ITS SAID END, IN THE HANDLE SO AS TO DISPLACE SOME OF THE SYNTHETIC RESIN THEREFROM AND BRING THE BOLSTER OF THE BLADE AGAINST THE UPPER 